Abstract
The effect of ammonium ions on growth and tylosin biosynthesis in Streptomyces fradiae NRRL 2702 cultured on a chemically defined medium was studied. Mycelial growth and tylosin production were not affected when ammonium sulphate was added to idiophase cultures to a final concentration of 10 m m or 20 m m; however, when ammonium sulphate was added to tylosin cultures to a final concentration of 20 m m before the onset of antibiotic biosynthesis (trophophase), tylosin production was severely suppressed while mycelial growth was stimulated. The activities of propionyl-coenzyme A carboxylase (EC 6.4.1.3) and methylmalonyl-coenzyme A carboxyltransferase (EC 2.1.3.1), enzymes involved in the synthesis of tylonolide precursors, were depressed in high ammonium cultures. The activity of macrocin 3′- o-methyltransferase, which catalyses the methylation of macrocin to form tylosin, was also affected by high concentrations of ammonium ions added in the trophophase.
Published Version
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